Lagarosiphon application
Image – Rohan Wells
An application to release the leaf-mining fly Hydrellia lagarosiphon (Ephydridae) as a biological control agent for the submersed water weed, Lagarosiphon major has been deferred. The suitability of an additional control agent is under study. This application may be lodged with EPA in 2021.
Background
Greater Wellington Regional Council makes this application on behalf of the National Biocontrol Collective, a consortium of regional councils and the Department of Conservation. The Collective funds the development of weed biocontrol programmes in New Zealand. Landcare Research is the science provider for this research. Richard Hill & Associates will prepare the application and manage all aspects of the application process on behalf of Greater Wellington Regional Council and Landcare Research. This includes consultation with EPA and other stakeholders.
Lagarosiphon major originates in South Africa and was presumably imported as an oxygen weed in aquaria. It has been naturalised in New Zealand since 1950. It is now distributed throughout New Zealand.
Its long fronds form vast underwater forests that cast deep shade. Shading smothers and excludes smaller native species. It roots readily from fragments and so can easily be carried between waterways on boats or other equipment. Broken fronds can clump in waterways, causing flooding. Rotting weed can turn water stagnant, killing fauna and flora. It blocks intakes in hydro lakes, and impedes navigation and recreational activities in many lakes. A 2011 estimate put the annual cost of controlling lagarosiphon in New Zealand at almost $1.5 million.
Hydrellia lagarosiphon is an aquatic fly, capable of laying eggs on stems below the water, and the larvae feed within the leaves. Impact studies in the laboratory showed that modest levels of larval feeding by H. lagarosiphon significantly affected biomass and the ability of damaged fragments to establish (Paynter 2013). Lagarosiphon is also a problem in lakes in Ireland and much of the developmental research has been conducted in Dublin. A related fly has achieved a good measure of control of the similar waterweed hydrilla in the USA.
The potential risks, costs and benefits resulting from the introduction of Hydrellia lagarosiphon have been formally identified and will be addressed fully in the application. A report will be found here once it is available:
- Potential beneficial and adverse effects of Hydrellia lagarosiphon
The key possible adverse effects are:
- the risk of direct damage to native plants
- indirect effects on flora and fauna as a result of disruption of ecological relationships
There are no native species in the same family as Lagarosiphon major. Extensive testing in Ireland indicates that the fly has a narrow host range, and evidence will be presented in the application that no native or desirable plants will be at significant risk in New Zealand. The eggs, larvae and pupae are found inside the plant underwater. No significant disturbance to existing ecological relationships is expected in New Zealand.
Consultation with Māori
The members of the EPA's national network Te Herenga will be contacted in July 2014, and invited to enter dialogue on the National Biocontrol Collective's plans to apply to EPA to introduce biological control agents to attack seven weeds. The applications will be submitted over the next 18 months.
The message to Te Herenga will describe how the applicant intends to assess the risks, costs and benefits associated with the proposed introductions. Members will be invited to identify any issues that they would like to be addressed in the application.
At the request of the applicant, EPA will convene a reference group from Te Herenga to meet and discuss the issues surrounding the proposed applications.
Consultations on previous applications to introduce biological control agents identified a range of generic views about the beneficial and adverse effects relevant to this technique. These views will be captured in the application along with specific comments related to this application and will be summarised here once available:
- Responses to consultation with Iwi Māori
Members of Te Herenga will be informed by EPA when each application is open for public submission, and will be able to comment on how the applicant has addressed issues raised during consultation.
Consultation with other organisations
- Responses to consultation with other organisations will be provided here once it is available
Key documents
Safety issues are paramount in the minds of biocontrol of weeds researchers. Researchers rigorously test all proposed agents to assess the risk of damage to non-target plants. A set of procedures was developed to help researchers choose a suitable shortlist of test plants, and this methodology is now well-accepted internationally (Wapshere, 1974). The technique is under constant review to update best practice (e.g. Sheppard et al., 2005; Briese, 2005).
The results of host range testing conducted in Ireland will be summarised in the application. The original data will be presented here once it is available. Interpretation of these reports will be peer reviewed, and the review will be supplied to EPA.
The feasibility of biological control of Lagarosiphon major in New Zealand has been investigated:
Cited references
Wapshere AJ (1974) A strategy for evaluating the safety or organisms for biological weed control. Annals of Applied Biology 77: 201–211.
Briese D (2005) Translating host-specificity test results into the real world: The need to harmonize the yin and yang of current testing procedures. Biological Control 35: 208–214.
Paynter, Q (2011) Feasibility of biocontrol of Lagarosiphon major in New Zealand. Unpublished contract report LC1234, Landcare Research. 19 p.
Sheppard AW, Heard TA, van Klinken RD (2005) Scientific advances in the analysis of direct risks of weed biological control agents to non-target plants. Biological Control 35: 215–226.